Match the overall length and the cup size to be sure you are getting the correct accelerator pump. The Inner Workings of the Quadrajet | Hemmings For Rochester Quadrajets pick up a idle mixture adjusting tool at most any part store. 360. Early Rochester four. Numbered bits are also available larger than #61- all the way to #1 (0.2280"). 1982 . When the engine fires up it should then immediately pull open about 1/16 to 1/8 of an inch via the engine vacuum and the choke pull off. Hello, I went out and started my 78 el camino today. Fast Shipping. Excessive priming, like an improperly adjusted choke, can cause flooding. Some Quadrajet builders of NHRA Stock and Super Stock Quadrajets do drill a third hole for accelerator pump travel but that's just part of getting the 21/32 maximum pump travel. Rochester's timeless Quadrajet four-barrel carburetor can perform with proper tuning controlled power piston used … Most performance enthusiasts shun the Quadrajet … Quadrajet Accelerator Pump; Quadrajet Adjustments; Quadrajet Choke Circuit; Quadrajet Float; Quadrajet Idle Circuit; Quadrajet Jets; Quadrajet Metering Rod; Quadrajet Needle & Seat; Quadrajet Rebuild; Quadrajet Secondary; Quadrajet Troubleshooting The secondaries open and there is the slightest amount of delay as the accelerator pump richens the mixture. The accelerator pump can also be used to prime the engine with fuel prior to a cold start. When discussing Quadrajet models, the number 4 means a four-barrel carburetor . 455.4hp, 494hp, 514hp, and currently over 550hp. It is a shorter style assembly that is great for performance applications. 323. 247 Posts . He also drills the accelerator pump discharge holes in the carb lid from 0.026 to 0.029 inch. • Hook up the throttle linkage and adjust for full throttle with someone depressing the gas pedal. When the linkage is accurately set, the circuit will begin to squirt fuel from the accelerator pump very soon after the throttle is opened even a small amount. This is when too much fuel and not enough air are present to support combustion. screw down the carb air horn with the two center screws. Operate the throttle linkage a few times to be sure nothing is binding. Comments: There are two holes in the accelerator pump lever arm for the lever arm rod to engage into: Inner and Outer. A hesitation or lag may result during this transition and influx of air. Tech Support. Accelerator Pump Rod Installed in Wrong Hole in Pump Arm Results in: Off-idle stumble or hesitation. the only way to buy the accelerator pump is to buy the whole rebuild kit. Correct for any Quadrajet application. REPLACING JUST ACCELERATOR PUMP IN A QUADRAJET Using a pump that has a short duration spring and a long stem so it can be trimmed allows you to set the pump cup just a tad above the fill slot. Adjust the float up or down by bending the small float support arms (tangs) on both sides, using a pair of needle nose pliers. "One of the most important things we modify is the idle circuit. Sep 18, 2006 #1. An accelerator pump is a component on a carburetor. The idle screws on a Rochester Quadrajet carburetor fine tune the air-fuel ratio going into the engine during idle. Usually, a faulty accelerator pump will result in a momentary lean condition, which can result in rough or sluggish acceleration, and even misfires. The secondaries open and there is the slightest amount of delay as the accelerator pump richens the mixture. A Quadrajet equipped car is often distinguishable from other cars by the sound of the engine as the secondaries open. 220/230 cam, world product heads, 9.5:1 compression, etc. BENEFITS OF BUYING DIRECT FROM EDELBROCK. Place the small gasket shield back on the air horn top. A minor clearance at curb idle between the arm and the adjuster is acceptable. "We also change the accelerator pump and install a larger needle and seat," Valdez adds. Carburetor Accelerator Pump Plunger #1982 for Quadrajet. Be the first to review this product. Is there an idle mixture adjustment like on other carburetors? STOP HERE and turn the carb over. If there is any problem with the pump, then there will be a problem in the fuel mixture during acceleration. Acc Pumps Complete Acc. The accelerator pump … There is a moment of quiet followed by a large increase in exhaust volume, sometimes described as a 'booming' noise. Messages: 726 Likes Received: 0. I rebuilt my Quadrajet this winter due to the secondaries not working properly. For this purpose, the carburetor has an accelerator pump. PHOTO 11 To make the adjustment, connect a hand-held vacuum pump to the choke pull-off and pump it up to 18 to 21 inches of mercury. Install the accelerator pump arm onto the rod, then position it so that a new roll pin can be pressed into the fulcrum hole. The outer hole produces a leaner pump shot, and can cause a lean stumble on engines requiring a robust pump shot. Skip to the end of the images gallery. Member; Posts: 224; Quadrajet accelerator pump problem « on: May 08, 2013, 08:55:24 PM » I have a poser for the group. ACCELERATOR PUMP ADJUSTMENT; AIR VALVE SPRING ADJUSTMENT The Rochester Quadrajet carburetor is a two stage, four-barrel downdraft. Consequently, is the Rochester quadrajet a good carb? Close the vent valve and open the primary throttle until the vent valve arm touches the bi-metallic strip next to the valve. Joined: Jan 6, 2006 Location: Texas. IDLE VENT ADJUSTMENT. The TPS plug must be absent for a Q-jet carb to be used on the street without a computer, however the feedback type Q-jet can be used in race only applications by removing the metering rods and changing the size of the primary jets. 322. Then take the reading using the method specified for your carburetor. . A Quadrajet carburettor car is often distinguishable from other cars by the sound of the engine as the secondaries open. A ... often the problem can be traced back to the accelerator pump system. I've got a 79 z-28 with some upgrades, nothing crazy. It fired up but idled high for a couple secs but just died.I tried giving it gas but it just idled high again and then died. Add to Wish List. FLOAT LEVEL ADJUSTMENT. For instructions any decent parts store should have a Q-Jet repair book. After you pump the accelerator yes it should snap closed all the way. Engine sputtering or stalling. If the old roll pin was not removed and you’re installing a new roll pin, remove the old pin first. Accelerator Pump Cup: Quadrajet 21/32 - This is FLUORELASTOMER a special purpose fluorocarbon-based synthetic rubber. Qty. The tool bends which will make adjusting easier. Arrow points to Dual Capacity Accelerator Pump plug; circled is where the TPS plug would be on an electronic or computer controlled Q-jet. • Have someone operate the gas pedal while you verify full throttle adjustment at the carburetor. Author Topic: Quadrajet accelerator pump problem (Read 8686 times) mikefam. Bend to adjust. CALL TO ORDER 888-799-1135. Make certain that it positively closes the throttle. Holley & Rochester Delayer Spring - 66-44. To adjust, open throttle so choke butterfly closes (when cold), connect a hand vacuum pump to vacuum choke pull off and pump it up both verifying the diaphragm is leak free and to cause the pull off to pull the linkage to the open/running position, and use a 1/4" drill bit to check the gap between the partially open choke butterfly and inside of carburetor air horn. There is a moment of quiet followed by a large increase in exhaust volume, sometimes described as a 'booming' noise. $34.95. Figure 30—Hot Air Choke System With Front And Rear Vacuum Breaks 356 323 320 Discussion Starter • #1 • Jan 10, 2012. Accelerator pump assembly, New ethanol compatible 2.57" Complete accelerator pump assembly with ethanol compatible cup and garter spring. I use a small seal puller to push the roll pin out, away from the choke housing. Place it on the base and mate the base to the float bowl. How much horsepower can a quadrajet support? It appears that the Quadrajet has variable orifice jets controlled by the metering rods, so that suggests it might not have low-speed idle jets used in other carburetors. Can anyone give me some direction? A 1/16" punch for removing the accelerator pump arm roll pin An adjustable T-square for setting float level A "pin vice" and a set of small numbered drill bits for measuring and making (or enlarging) small diameter holes. After the adjustment, put your fingers on the pivot and needle and check the measurement again. The accelerator pump orifice is also plugged. Some pull-offs had an adjustment screw, while some older carburetors require the linkage to be bent to achieve the proper opening. If it's not closing all the way on a cool engine, you can adjust it from the passenger side of the car. Install the two metering rods down into their small barrels and attach the small support arm that holds them in position. Incorrect adjustment is the typical culprit. When divorced, a linkage connects the spring to the choke plate. We stock complete accelerator pumps, replaceable cups and springs. The Edelbrock Hi-Perf Accel Pump & Spring kit. The most common cause of rough idle quality in engines equipped with this carburetor is an unevenly adjusted idle mixture circuit caused by incorrectly adjusted mixture screws. quadrajet adjustment help - backfiring/popping Discussion in 'Troubleshooting & Diagnosis' started by 79silverz28, Sep 18, 2006. Transitions Via The Accelerator Pump. The carb is completely rebuilt including new throttle valve bushings and runs great. Three different styles of pump cups were used, but all Rochester Quadrajet carburetors use a 21/32" pump cup OD. 425. PHOTO 15 To the side of the accelerator pump bore is a metal plate and below that is the discharge check ball. Quadrajet adjustment for accelerator pump. 79silverz28 Veteran Member. Also put in a new accelerator pump … The accelerator pump is supposed to provide additional fuel needed during acceleration. quadrajet idle adjustment, Fast Idle Adjusting Screw B-09249 B-09251 c D. E. 320. In Stock. Anytime the throttle is opened, there is a transition time required for the carburetor circuits to operate. It is commonly found on many older vehicles that are equipped with carburetors. Skip to the beginning of the images gallery. Jennings did mention that ethanol/alcohol will cause an AFB carb's leather accelerator pump to peel up over time. I've rebuilt more Q-jets than I can remember and have never seen anything like this. Measure the distance between the top of the choke valve wall and the top of the pump stem. Check the gasket used between the float bowl and the base as you did for the air horn/float bowl unit. They are bought typically in sets numbered from #61 (0.0390") to #80 (0.0135"). Ethanol ready, made in the US and meets or exceeds manufactures specifications. Products [16] Item In Cart. Rods / Linkage Pulloff Rod. The accelerator pump (A) sends additional fuel through a dedicated circuit to the discharge nozzle (B). • Check for interferences at the accelerator pump linkage. • Install a good throttle return spring. Rochester Products produced many different varieties of accelerator pumps for the Quadrajet carburetor. Rochester Quadrajet accelerator pump catalog. For proper accelerator pump discharge (Olds engines) always use the inner lever arm position. What's the difference between square bore and spread bore? I adjusted the float to specs, pulled it up about 1/8th inch higher than it was. Is the accelerator pump adjustable? It has wide chemical resistance and superior performance, especially in high temperature : 1309CP: $10.49: Availability: Check: Complete Acc. In stock. The “M” after that, is a style/model type. Every time the float bowl is removed and replaced, this accelerator pump adjustment should be verified. Most differences were due to minor changes in pump plunger stem lengths and compression spring heights. Remove the idle vent valve cover from the air horn, if so equipped. This assembly is 2.57" long. SKU.
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